The present invention relates generally to sectional overhead doors commonly used to selectively close openings in residential and commercial buildings. More particularly, the present invention relates to sectional overhead doors that are designed to withstand substantially greater wind-loading conditions than conventional doors. More specifically, the present invention relates to design features that may be incorporated in or added to sectional overhead doors to resist damage from extreme wind-load conditions or to at least minimize damage to such an extent that a door so configured remains operative after excessive wind-loading conditions.
Due to the relatively high incidence of severe weather conditions where high winds have caused a considerable amount of damage to residential and commercial structures, there has recently been a greater awareness that door systems, if strengthened, could prevent damage to the structures. This can have the effect of greater safety for occupants of the structure in terms of a reduced likelihood of injury to the occupants, as well as providing an avenue for escape from the structure, if necessary. Building code officials have been influenced by this public awareness, as well as by insurance company interests, to increase building code requirements for resistance to high wind-velocity pressures to reduce damage, loss of property, and loss of lives. Thus, the wind-load requirements for overhead sectional doors in higher risk areas are in the process of being, or have been, increased.
Over the years attention has been given, due in part to code requirements, to increasing resistance of doors to wind-velocity pressures. Most commonly, these efforts have resulted in proposals for increasing the thickness of the door and/or adding trusses and beams to the back or inner side of the door as strengthening members. Due to conservation of material considerations, supplementing strength has normally taken the form of beams and struts that are attached to and extend horizontally of the door structure on the inner face of the door. Such beams and struts are designed to create a stiffer or more rigid door section by positioning them such that the stresses generated by wind-velocity pressures against the door section are transmitted to the beams and struts and subsequently to the jambs, header, or even the floor of the building as stress forces operating primarily parallel to the direction of the wind. These beams and struts are variously made of materials such as solid wood beams and U-shaped or C-shaped channels of steel. As these components are normally sizeable, they have significant weight, and to provide adequate reinforcement, it is common to employ six to eight beams or struts on a door.
The use of such beam or strut-reinforcing members is disadvantageous in numerous respects. The weight of the beams, along with the components necessary to effect attachment to the door, often doubles or triples the weight of the door. The cost of the beam and strut materials is normally quite high due to the size and weight of the components involved. The substantial additional weight also makes a door more difficult to install and necessitates two installers. Further, struts and beams are commonly two to six inches in height and, thus, protrude a substantial distance from the inner surface of the door, such that they are aesthetically unsightly and take up space inside the building. As a result, additional clearance is required when closing the door behind a vehicle, and when the door is in the open position, the beams protrude downwardly into the headroom area to an extent that may prevent the parking of taller vehicles, such as sport utility models, in garages having relatively limited overhead height.
A main operational disadvantage of using conventional beams and struts is that an adequate number of the substantial size normally employed causes the door to become rigid by adding beam strength to the door panels. As a result, the bending moment operative on the panels when wind loaded puts one side of a door section into greater tension and the other side of the door section into greater compression due to the greater size and thus greater moment arm created by the beams. This achieved rigidity, therefore, does not allow the door to flex without severely compression loading one side of the door section, which leads to the failure of the door sections by way of buckling. When buckling commences, the first thing that fails is the channels or struts, which rupture dramatically, thus causing the door sections to become permanently deformed, normally to such an extent that the door will not operate. This is because the substantial sized channels, struts, or bars used to prevent failure are of sufficient strength such as to preclude recovery adequate to allow the door to be operable once buckling occurs.
Another type of design that is employed to resist wind load in doors is referred to in the art as windlocks. Windlocks are locking devices located on the end portions of door sections that lock the door to the track system or to the jamb when the door is closed. Windlocks allow stresses generated by wind-velocity pressure that is exerted on door sections to be transferred to the doorjamb or other building structure. Windlocks have been employed primarily in relation to rolling doors since the slats of a rolling door cannot feasibly be reinforced with beams or struts because they would interfere with or render excessively large the rolled up condition of the rolling door when it is in the open or stored position. Further, with the narrow slat configuration necessarily employed in rolling doors, sizeable beams or struts are impractical and would create the possibility of binding or jamming of the door in the stored position. Efforts to employ windlocks on sectional doors require accurate alignment of the interengaging elements; otherwise, interference can readily occur. In addition, only a very limited number of windlocks can be employed on the jamb of a conventional sized door without the necessity for employing oversized reinforcing elements or intricately-configured interconnection elements.
Another design area for reinforcing sectional overhead doors that has gained interest in recent years relates to the utilization of vertical reinforcing posts. In such designs, a plurality of vertical posts are provided that divide the horizontal span of the door into reinforced areas with increased rigidity, and the wind-velocity pressure loads are transferred to the floor and the header above the door. Some of these designs employ vertical posts that can be retrofitted to an existing door but render the door inoperable after installation. These vertical post designs, if permanently attached to the door, add additional weight to be counterbalanced and also protrude into the interior space in the closed and opened positions in the same manner as horizontal struts or bars. Since vertical reinforcing posts require attachment to the header of the garage door opening, problems may be presented, particularly in retrofitting, because in many instances, garage door headers are not structurally designed to accommodate stresses of the magnitude that may be imparted. Similarly, the bottom of the post must be attached to the floor, and in many cases, the foundation is not designed to handle the stresses that may develop, which can result in cracking of the foundation slab. In the instance of dirt floors in a building, it is necessary to pour pilings in the floor to provide an adequate anchoring point for such vertical post anchoring. In some instances, the floor-anchoring structure protrudes above the surface of the floor and, thus, becomes a surface obstruction in the floor. In instances where holes are provided in the floor to effect engagement with the vertical posts, the holes may collect dirt or debris, thus rendering them inoperative for their intended purpose.
In longer door applications, header locks have been employed primarily to preclude separation of the door from the header during wind loading. Conventionally, these header locks take the form of opposed flat plates that move into overlapping, parallel but spaced relation when the door moves into the closed position. As a door deflects under wind loading, the header lock engages and limits further deflection of the top door panel in the area where the header lock is mounted. Such header locks also prevent the top door panel from rotating, which is an inherent tendency due to the substantially greater deflection of a door proximate its horizontal and vertical medial area. As a result, torsional stress concentrations may be created in the areas where such a header lock attaches to the door, whereby otherwise premature buckling of the panel may occur.
Therefore, existing approaches to the reinforcement of sectional overhead doors to withstand high wind-velocity pressures, both positive and negative, have embraced the concept of reinforcement of the door sections to render their construction as stiff or rigid as possible. This is coupled with the usage of beams, bars, or posts of substantial dimension, which, in varying fashions, transmit stresses to the jambs, header, or floor of the building structure proximate to the door. These existing wind-resistant systems have all embodied sufficient limitations and/or disadvantages, such that no existing structures have achieved widespread acceptance in the industry.
Accordingly, an object of the present invention is to provide a wind-resistant sectional overhead door wherein the door sections are tensioned by utilizing one or more of the tensile strength of the steel skins or outer steel skin, the core, and the inner substrate as may be incorporated in a door as flexible members that transfer the windimparted forces to the guide rollers, roller track, and jambs of a door opening. Another object of the present invention is to provide such a door wherein the door sections are tension loaded, and preferably pre-loaded, when the door is in the closed position. It is a further object of the present invention to provide such a door wherein the structural elements of the door are closer to the centroid of the section profile, such that the bending moment produced by wind forces acting on the door produce less compression in the door section components. Yet another object of the present invention is to provide such a door wherein the door sections retain their flexibility due to the absence of reinforcing members, which permits the door to undergo substantial elastic or flexible deformation, either outwardly or inwardly, as a result of negative or positive pressures, respectively, yet to return sufficiently close to the original configuration such as to remain operable after high wind-loading conditions.
Another object of the present invention is to provide a wind-resistant sectional overhead door wherein the wind-load components can be factory installed and shipped in the door packaging without additional packaging requirements. Yet another object of the present invention is to provide such a door that is a standard door with a separate wind-load kit that may be employed where necessary to meet requirements of building codes, which may vary due to location, even within relatively small geographic areas. Yet another object of the invention is to provide such a door having wind-load features that can be added to different door constructions to provide different levels of wind-load protection as a result of different structural characteristics of the basic doors. Still a further object of the present invention is to provide such a door wherein fewer parts are required to construct a wind-loaded door in terms of both major components and hardware, fasteners, straps, and the like. Still another object of the present invention is to provide such a door that can be installed in less time than conventional wind-load doors and reduces manpower requirements to a single installer.
Still a further object of the invention is to provide a wind-resistant sectional overhead door that is of substantially lighter weight than conventional wind-load doors, thereby resulting in reduced shipping and handling costs. Yet another object of the present invention is to provide such a door wherein the reduced weight permits the use of conventional counterbalance systems for lightweight doors. Still another object of the present invention is to provide such a door that, although employing standard track and hinges, is of substantially lesser weight than a conventional wind-load door, which results in retention of operational longevity. Yet a further object of the present invention is to provide such a door that may employ plastic rollers rather than heavy-duty steel rollers, which are conventionally employed for wind-load door configurations.
Another object of the present invention is to provide a wind-resistant sectional overhead door having a header lock that avoids stress concentrations and prevents premature buckling of the door, thereby increasing the probabilities of maintaining the integrity of a building during high winds and reducing the probabilities of the need for replacing a door in whole or in part. Still another object of the invention is to provide such a header lock for a door that is operative any time the door is closed and the components do not significantly protrude into the building space. Yet a further object of the invention is to provide such a header lock for a door that is low cost, can be factory installed on a door, and can be shipped without the necessity for additional packaging.
Yet a further object of the present invention is to provide a wind-resistant sectional overhead door that is safer in numerous particulars than conventional wind-load doors. Yet a further object of the invention is to provide such a door that is always wind-load active when it is closed and requires no action by a building occupant to prepare or activate the wind-resistant features of the door for high wind conditions. Yet a further object of the present invention is to provide such a door wherein components of the door do not protrude into the building, thus reducing risk of injury to people or damage to vehicles or other objects within the building, as well as providing more space for vehicles of larger dimensions. Yet a further object of the present invention is to eliminate the safety hazard of conventional wind-load doors produced by beams or struts, which may be misused as standing or gripping elements, particularly by adolescents. Yet a further object of the present invention is to provide such a door that avoids surges normally produced by a heavy door, which may require unsafe full force adjustment of a door operator to prevent reversal when closing the door.
In general, the present invention contemplates a wind-resistant sectional overhead door selectively moveable between an open position and a closed position relative to a door opening defined by spaced vertical jambs and a horizontal header extending therebetween including, a plurality of elongate horizontal panels pivotally connected at the top and bottom edges of adjacent of the panels, roller tracks mounted on the vertical jambs to either side of the door, roller shafts mounted at the ends of the panels, guide rollers carried by the roller shafts and engaging the roller tracks, and restraining members for limiting axial movement of the roller shafts, whereby the roller shafts and the panels are tension-loaded when the door is in the closed position to prevent buckling of the panels under applied wind forces. Another facet of the present invention contemplates a header lock for interconnecting the top panel of a sectional overhead door to the header of a door frame including, a panel bracket attached to the top panel of the door, a header bracket attached to the header of the door frame, an extending arm on the panel bracket having a curved section with a first engaging surface, a return arm on the panel bracket having a second engaging surface positioned rearwardly of the first engaging surface permitting pivotal movement of the top panel of the door relative to the header while restraining separating of the top panel from the header.